Analysis of the brain of linebacker Junior Seau, who played 20 seasons in the NFL, showed that he had a degenerative brain disease. Symptoms include memory loss, aggression, confusion and depression. Seau committed suicide by shooting himself in the chest.

As National Football League teams prepare for the next round of the playoffs, the NFL is bracing for a legal showdown with potentially much higher stakes: lawsuits by more than 4,000 former players and families claiming the league concealed information about the dangers of repeated head injuries.

New findings that onetime star linebacker Junior Seau had a degenerative brain disease when he killed himself in May have turned up the heat on the NFL, which claims it's doing its best to protect players and support medical research.

The suits, awaiting review by a federal judge in Philadelphia, could be a replay of the tobacco cases - the long-running and ultimately successful claims by smokers and state governments that the industry hid the lethal risks of its products.

But there are also differences that, some analysts believe, will make the players' cases more difficult.

Among other things, the evidence of danger and deception was clearer in the smoking cases than it is in the suits against the NFL. The league may have an argument that the players understood the risks they were taking, in contrast to smokers' claims that the tobacco industry kept them from learning the truth until it was too late.

Courts vs. arbitration

And the league, by relying on its teams' contract with the players' union, may be able to shift the forum from the courts to private arbitration, where damages are limited.

The concussion suits nevertheless have potentially huge consequences, both for the NFL's finances and for its safety policies, in light of mounting evidence of the cumulative effects of years of violent gridiron collisions.

The plaintiffs include relatives of two players who committed suicide: Dave Duerson, a former defensive back for the Chicago Bears - whose February 2011 suicide note said, "Please, see that my brain is given to the NFL's brain bank" - and Ray Easterling, a former safety for the Atlanta Falcons. Seau's family has not said whether it will join the suits.

Seau, who never had a reported concussion in his 20-year career, suffered from a brain disease called chronic traumatic encephalopathy, or CTE, National Institutes of Health researchers said last week. In response, the NFL told USA Today that the finding "underscores the recognized need for additional research to accelerate a fuller understanding of CTE." The league said it has donated $30 million to medical research.

Such comments are reminiscent of the response by tobacco companies to the first expressions of public concern about smoking in the 1950s, said Stanton Glantz, a UC San Francisco professor of medicine, former government health consultant and longtime adversary of the tobacco industry.

Reassuring statements like "we need to do more research" and "we're studying it" helped tobacco companies fend off liability for decades, Glantz said.

It was only in the 1990s, when evidence conclusively established that the companies had knowingly concealed the dangers of their products, that they were hit with multimillion-dollar damage awards in suits by smokers, and with state lawsuits that led to a nationwide $206 billion settlement in 1998, said Robert Rabin, a Stanford law professor.

Tobacco's cover-up

At first glance, Rabin said, the tobacco and football suits look similar: Both groups of plaintiffs had known they were taking some risks but said they were unaware of the dangers that the tobacco companies, and the NFL, concealed from them.

But he said the tobacco suits were strengthened by the addictive nature of cigarettes, making it harder to quit even when smokers learned of the mortal risks, and by the now irrefutable medical evidence.

By comparison, Rabin said, "in the NFL cases, causation is likely to be very difficult to establish in individual cases." Proving a claim may depend, he said, on how many concussions or other injuries a player suffered, how far apart they were in time, and how the team and the league responded or could have responded.

Brian McCarthy, a spokesman for the NFL, denied that the league has tried to mislead players and said it has taken "many actions to protect players and advance the science and medical understanding of the management and treatment of concussions."

That assertion may be tested in a jury trial. But the NFL would prefer to move the dispute out of the courts and into arbitration, relying on precedent established in another case that arose from a fatality.

After Korey Stringer, a Pro Bowl offensive tackle with the Minnesota Vikings, collapsed and died from heatstroke at a summer training camp in 2001, his widow sued the league for exposing him to dangerous conditions in mandatory heavy equipment without proper medical supervision.

A federal judge sent the core of the case to arbitration in 2007, saying the dispute called for an interpretation of the qualifications and duties of team trainers and physicians, subjects of arbitration under the NFL union contract. The league later settled the suit on undisclosed terms.

Two other judges have used similar reasoning in separate NFL concussion cases, said William Gould, a Stanford labor law professor and former chairman of the National Labor Relations Board. If the judge in Philadelphia sends the 4,000-plus suits to arbitration, he said, the NFL will be "in the driver's seat," with potential damages limited and the focus on the actions of individual teams, players and trainers instead of the league.

But Gould said there's a difference between the Stringer case and the concussion suits that should weigh in the players' favor: their argument that the NFL deceived everyone, including the teams' trainers and doctors, about the long-term effects of repeated head injuries.

"The players say it doesn't matter what kind of care the trainers showed," Gould said. "The NFL was in a position to know something about it and they withheld information."

If that's a legitimate issue, he said, it's a dispute about alleged fraud, not contract interpretation, and should go to a jury, not an arbitration panel. That jurisdictional question, Gould said, will probably take a couple of years to resolve.